1. Field of the Invention
The present invention relates to heat exchangers, and particularly to a hydro-blasting anti-withdrawal device support for mounting a hydro-blasting anti-withdrawal device in the proper position for cleaning heat exchanger tubes, particularly for shell-and-tube heat exchangers where the tube sheet is recessed from the end of the shell.
2. Description of the Related Art
Shell-and-tubes heat exchangers are commonly used in oil refineries and petrochemical plants. The shells are elongated, cylindrical outer casings. Bundles of tubes are supported within the shells and extend from one end of the shell to the other. The tubes are secured to holes in the tube sheets at opposite ends of the shell (for linear tubes; U-tubes may be secured to a single tube sheet at one end of the shell) by welding or by rolled mechanical joints. A first heat exchanger fluid circulates through the tubes and a second heat exchange fluid circulates through the shell outside the tubes for heat exchange. The ends of the shell are typically covered or capped by channel heads that direct the flow of fluid in the tubes, the heads being bolted or secured to a shell flange.
From time to time, flow through the tubes may be restricted or impaired by corrosion or by the settling of solids in the tubes, which reduces the efficiency of the heat exchanger and may require a plant shut-down for cleaning the tubes. Cleaning heat exchanger tubes positioned within a heat exchanger is a practice in the petrochemical industry that requires absolute precision. Accordingly, such a process is often undertaken with the use of a hydro-blasting machine and an anti-withdrawal device. Hydro- or water-blasting is a cleaning method that utilizes a highly-pressurized stream of water to remove old paint, chemicals, or the build-up of coke, solidified carbon, or even metal, without damaging the underlying structure. The pressurized stream of water is delivered through a hose and a lance (which may be rigid or flexible) inserted into the tube. Since the pressurized flow may result in back-pressure that forces the lance back out of the tube, the lance is usually secured by an anti-withdrawal device for the health and safety of workers cleaning the tubes. Flushing each heat exchanger tube with such a highly-pressurized and sometimes extremely hot, stream of fluid can prevent or reduce the accumulation of contaminants within each heat exchanger tube, which might otherwise limit the flow of fluids through each heat exchanger tube, and thereby allows for efficient operation of the heat exchanger.
In some heat exchangers, the tube sheet is positioned adjacent to the end of the shell or outer casing of the heat exchanger. This allows the anti-withdrawal device to be clamped to the shell flange while an adjustable arm clamps or locks the hose within an inch or two of the tube sheet with the lance extending into the tube.
In other heat exchangers, however, the tube sheet is recessed within the shell, such that the anti-withdrawal device cannot be mounted to place the adjustable clamping arm in close proximity of the tube sheet. The greater the distance between the hose and the tube sheet, the greater the chance that the lance may withdraw from the tube and seriously injure the person cleaning the heating tubes of the heat exchanger.
Thus, a hydro-blasting anti-withdrawal device support solving the aforementioned problems is desired.